Method of producing coke



Patented Oct. 25, 1932 UNITED STATES,

PATENT OFFICE FRANK WALTER STEERE, OF SCABSDA'LE, YORK, ASSIGNOR TO THE BARRETT COM- PANY, OF NEW YORK, N. Y., A CORPORATION OF lZ-E'W JERSEY METHOD OI PRODUCING COKE 7N0 Drawing.

This invention relates to improvements in the operation of by-product coke oven plants whereby the maximum yield of merchantable coke can be produced, together with other valuble by-products.

In the operation of coke oven plants the coke is delivered from the ovens in an incandescent state and it is necessary to cool it as quickly as possible to avoid combustion with 10 consequent loss of coke. This cooling is commonly efiected by quenching with water. The coke, after cooling, is classified into the various sizes required by the trade. It must in some cases be crushed to eliminate larger 15, lumps andto provide higher yields of definite sized pieces. The grading of the coke into difi'erent sizes is accomplished by a screening operation. During the quenching, screening and handling of the coke some of it is broken up or degraded into pieces too small to be marketed as commercial coke products. Such coke is commonly knownas breeze. When crushing is resorted to the percentage of breeze will in general be higher than when the coke is not crushed. In general, all coke which will pass through a threequarter inch mesh screen is included as coke breeze, although in some cases only the coke particles passing through a half inch mesh 0 screen are so designated. The amount of coke breeze passing through a three-quarter inch mesh screen will ordinarily amount to around four to six percent of the coke produced but may in some cases run to a higher amount, around ten percent or higher.

" Coke breeze in general finds no market and it is commonly disposedof by burning it as fuel, for which purpose its value is far below that of merchantable coke.

It has been proposed to convert coke breeze into marketable fuel by briqueting it with various binders, but this requires the grinding of the coke breeze to produce uniform sizes of particles suitable for briquetting,

and the subsequent forming of the ground coke breeze into briquettes by a briquetting operation. This grinding of the coke breeze, in addltion to 1ts expense, s ob ect1onable because of the wear and tear on the grinding equipment, with the result that the grinding Application filed February-1, 1928. Serial No. 251,233.

and briquetting of coke breeze has been carried out only to a limited extent.

Coke breeze has also been added to the coal charged into coke ovens (see United States patent to Graul, No. 1,308,754). The coalcharged to coke ovens 1s commonly ground and in many cases is pulverized before it is charged to the ovens in order that it may be in the form of fine particles when charged; and the coke breeze employed has similarly been employed in the form of fine particles charged with the finely divided coal.

Coke breeze can be crushed or ground and converted into fine particles similar to those of the coal charged to the coke ovens, but the wear and tear on the crushing apparatus is excessive, and the cost and difiiculty of grinding or crushing the coke breeze to produce uniformly small particles out-weighs to a large extent the advantages resulting from returning the coke breeze to the coke ovens.

The present invention provides an improved process of operation of by-product coke oven plants whereby the coke breeze can be advantageously utilized for the production of merchantable coke, and whereby only gas, merchantable coke and by-products need be produced at a coke oven plant.

According to the present invention the cokebreeze, without crushing and containing not only the finer particles but also the larger pieces which pass through a screen of around one-half to three-quarters inch mesh during the screening operation, is added to the coal charged to the oven, and the admixed coke breeze and coal are subjected to coking. By operating in this way, all of the coke produced can be sold as merchantable coke, that returned to the coke ovens as breeze being combined with the coal on coking to form merchantable coke and the coke breeze therefrom being returned in a similar way in further operation.

The coal employed'in the coke oven operation, where the coke breeze is added to and admixed therewith, should be a coal having sufficient coking properties and constituents to cause the coke breeze to become blended therewith. Domestic coke is commonly produced from coal rich in volatile and coking constituents in order to produce a larger amount of merchantable-gas from the coking and gas making operation. With rich gas making coal the coke breeze will be blended I ously with the coking of the coal, and gives a composite product containing pitch coke as well as coke breeze combined with coal coke.

When pitch is employed in the present process, it can be readily produced by the dis tillation ofthe tar separated from the coke .oven gases in the by-product recovery system of'the coke oven plant. This by-product tar,

' from heavy tar and pitch constituents by on distillation, ylelds merchantable oils and a pitch residue. By returningthe pitch resi due to the coke ovens in admixture with coke breeze and coal it is subjected to destructive distillation in the coke ovens and converted in part into pitch cokeand in part into gas and tar. By utilizing all of the tar produced at the coke oven plant in this way, the plant can be operated so that only salable products,

namely, merchantable coke, gas, coal tar distillates and such roducts as ammonia and/or light oil, are pro need at the coke oven plant. The distillation of the tar to produce therefrom salable oils can be carried out in ordina tar stills, but is more advantageously carrie out by distillation of the tar by direct contact with hot coke oven gases. The gases employed for thedistillation may be freed scrubbing with hot pitch or by cleaning with an electrical precipitator. Clean salable coal tar oils maybe recovered when the gases carrying the oil vapors are subsequently cooled 4 mixture to the coke ovens,

or around 400 F., or in some cases even to condense the oils. The distillation of the tar can be carried to a. point such that pitch of high melting point is produced, with a hi gh yield of marketable oils. The pitch may, for example, have amelting point around 300 F.,

higher. The total pitch produced from the tar can be returned to the coke ovens along with the total amount of coke breeze. Additlonal pitch may, however, be employed such as may be produced by the distillation at the coke oven plant of tar from outside sources.

In mixing the coal and coke breeze, or coal, coke breeze and pitch, before charging the the mixing operation is conducted without passing the coke breeze through the. ulverizer for the coal. The coke breeze may be supplied continuously 4 whatless than 0 neonate in regulated amount along with the coal and pitch to the mixing bin.

The coke breeze can advantageously first be admixed with the pitch before the admixed I coke breeze and pitch are mixed with the coal. A particularly advantageous formof preliminary. admixture of the coke breezeumd pitch duces pitch coke within the pores of the cokeparticles and on the surface thereof, thus assistin in, binding the coke breeze particles to the co e produced from the coal.

The proportions of coke breeze and pitch blended with the coal charged to the coke ovens can be varied. In some cases the amount of coke breeze produced will be only around five or six percent or less of the total coke produced, while in other cases it may be as high as 10% or more of the coke roduced. The amount of pitch employed may e around one percent or somewhat less of the coke oven charge or it may be increased to several percent, e. g., ten to fifteen percent, particularly with high melting point pitch, e. g., around- 400 F., melting point.

When pitch is added to the charge it serves as a coking constituent for the breeze, supplementing the coking constituent of the coal,

that is, the pitch serves as a flux or binder for the coke breeze particles and aids in binding them to the coal coke produced and tends to give a more uniform structure, particularly where the pitch is admixed and combined with the coke breeze before they are admixed with the coal of the charge.

The coking of the composite charge can be carried out in the usual way. During the coking operation the coke breeze will remain practically inert, but the pitch will liquef'y and become coked to form pitch coke and the coal will also be coked in admixture there.-

with. The composite coke produced will contain the coke breeze, including pieces of coke breeze up to, for example, one-half or threequarter inch size, distributed throughout the coke product, which will also contain pitch coke produced from the pitch charged to the oven.

In the operation: of coke ovens containing e. g., around five or ten percent of coke breeze and containing e. g., one to five per cent of pitch'of 300 F. or 4 0O F. melting point, the tar produced r ton of coke may be somemarily produced from coalto which no coke breeze is added. The yield of tar per ton of coal coked will, however not be. chan materially. The coking oi the pitch wil result in destructive distillation and the driving of! of part of the pitch as and as oil or tar constituents which will collect-ed with the gas and tar from the distillation'of the coa The com osite tar so produced can be subjected to d stillation for the production of marketable distillate oils, such as creosote oils, and to produce additional pitch for use in the further carrying out of the rocess. I w This met od of o ration utilizes all of the coke breeze pro uced at the coke oven plant and utilizes all of the tar produced at the coke oven plant, with the production of coke, distillate oils and gas as the only primary products, together with such byproducts as ammonia and light oils. A coke oven plant operated in this way produces only merchantable roducts and a greatly increased yield of mar etable coke from the coal employed. The fuel for the boilers or for otherpurposes now commonly provided by burning the coke breeze can be supplied from other sources such, e. g., as water-gas machines or as producers.

When pitch is not added to the coke oven char e coking constituents of the coal will relied u on to bind the particles of coke breeze to t e itch coke roduced and, as above stated, wit some coa rich in coking or volatile constituents, considerable coke breeze can be added without crushing and incorporated in the coal coke produced.

The present invention is of particular value for the production of domestic coke. Whereas in metallurgical coke operations, large pieces of uniform structure are desira e,

1 mum!!! so resIulting charge. h Mr I Ex 11 testimon e m this is not the case when he coke is being made for domestic use, where large pieces are a disadvantage in that they have to be crushed, Any lack of uniformity of the coke roduced by the resent lIlVGIltlOIllS thereore unobjectiona 1e in domestic coke, and such weakening of the coke structure as may be brought about by the presence therein of the particles of coke breeze of varying sizes up to around e. g., one-half or three-quarter inch size is of advanta in reducing the amount of crushing required to convert the coke into domestic sizes.

The present invention is not limited to the use of the smaller coke particles commonly included as coke breeze, since pieces of coho. somewhat larger than those" ordinarily included in coke breeze can be returned to the coke oven charge in a similar way. Accordingly, where the market rice of the smaller sizes of coke is sutlicien y below that of the lar r sizes, the smaller sizes can be returned to t e coke oven in admixture with the coal, I or with coal and pitch,-and thereby ipcorporated in the coke charge produced. The 

